How to convert macOS Extended Journaled to APFS?

Solution 1:

This site has instructions on how to convert your drive to APFS.

1. Restart the Mac into Recovery Mode.
2. Launch Disk utility.
3. Click-select your named boot volume. (Not the physical drive above it.)
4. In the Disk Utility Edit menu, select “Convert to APFS

More detailed instructions are given in the link above.

Solution 2:

How to convert your drive to APFS:

• Restart the Mac into Recovery Mode.
• Launch Disk utility.
• Click-select your named boot volume. (Not the physical drive above it.)
• Click "Deactivate" Toolbar item. <- This enables the Menu item below!
• Select "Convert to APFS" from the Edit menu.